The present invention is related basically to the field of earth excavators and more particularly to that area of the field concerned with such excavators that utilize a bucket wheel arrangement to dislodge and remove earth to a specified grade and, using in conjunction therewith, one or more crumbing blades.
Excavating machinery, particularly such machinery utilizing a bucket wheel form of earth removing means, are typically unidirectional since they are capable of operating only when moving in a forward direction. Thus, at the end of each elongated swath taken, the machine must be moved back to its original starting place before beginning the next successive swath. It has become desirable to obtain some form of excavating machine including the advantages inherent in a bucket wheel type excavator that is also capable of operation both in forward and rearward longitudinal directions. This desirable feature is provided by the present invention in a pair of retractable crumbing blades. The blades are located on opposite sides of the digging or excavating wheel and are independently operable to extend to operative positions. Each blade includes a scraping edge that is located in a plane substantially tangential to the bottom of the cutter periphery (when operative). Each is also movable to a retracted position clear of the wheel and ground surface being operated upon. In operation, either crumbing blade functions to scrape along the ground directly behind the digging wheel to catch and refeed loose material to the buckets of the digging wheel. The operative blade also forms a relatively smooth finished surface behind the machine. Functionally, the crumbing blade acts similarly to the blade of a surfacing machine or grader. Since two of the retractable blade assemblies are provided one on each side of the digging wheel, it is possible that a leveling and loose feeding function may be performed regardless of whether the machine is moving in a forward or rearward direction.
U.S. Pat. No. 2,782,535 to R. Fuller et al granted Feb. 26, 1957 discloses a ditching machine that makes use of a fixed form of crumbing blade assembly. The blade assembly set forth in this patent is exemplary of the general form of such blades as commonly known in the industry. The blade is fixed to a supportive framework and follows behind a rotatable digging wheel. The purpose for the blade is to catch loose material and refeed it to the digging wheel while forming a relatively smooth, accurate surface behind the machine. A similar, stationary form of crumbing blade is illustrated in U.S. Pat. No. 2,088,369 granted to B. H. Flynn on July 27, 1937. Again, the crumbing blade in this machine is fixed to a supportive framework and operates in response to movement of the machine and operation of an associated digging wheel in a prescribed forward direction. Several different forms of the stationary blade disclosed in the Flynn patent are utilized to complement the shape of the cutting wheel.